/etc/hosts file

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This topic contains 2 replies, has 2 voices, and was last updated by  Swapnil Patil 1 year, 7 months ago.

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  • #33359

    Swapnil Patil

    I am confused with whether /etc/hosts file of all datanodes should contain IP of every datanode in the cluster?
    Do datanodes communicate with each other in the network? and if yes why?
    Hoping for the response
    thanks in advance

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  • #33477

    Swapnil Patil

    @ Hesam
    Thanks alot for your reply..


    Yes! in order to send replication messages to each other,datanodes should know each other.

    As an example,when block #1 of data is going to be replicated on nodes 3,6,9 (data nodes on which block is going to be written are selected by NameNode), client machine sends the first node in the list of suggested datanodes(list provided by namenode) a message to inform that it is going to send a block of data.and also the list of other selected data nodes are transmitted via this message.the first datanode sends the 2nd datanode a similar message,and 2nd sends 3rd datanode(and so on… if more data nodes are selected) and the last datanode,sends back a message “I am ready” and then each data node sends back their previous datanode an “I am ready” message.when the first data node recieves that message,replication from client to first node starts.and when replication to first node completed,replication to 2nd starts from 1st node,and so on…

    You can read about the whole process here ;-)

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